/**
 * (C) Copyright IBM Corp. 2010, 2015
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 */

package com.ibm.bi.dml.runtime.controlprogram.parfor.stat;

/**
 * Helper class for encapsulated time measurements.
 * 
 * 
 */
public class Timing 
{

	
	private long _start = -1;
	
	public Timing() {
		//default constructor
	}
	
	public Timing(boolean start)
	{
		//init and start the timer
		if( start ){
			start();
		}
	}
	
	/**
	 * Starts the time measurement.
	 */
	public void start()
	{
		_start = System.nanoTime();
	}
	
	/**
	 * Measures and returns the time since the last start() or stop() invocation and
	 * restarts the measurement.
	 * 
	 * @return
	 */
	public double stop()
	{
		if( _start == -1 )
			throw new RuntimeException("Stop time measurement without prior start is invalid.");
	
		long end = System.nanoTime();		
		double duration = ((double)(end-_start))/1000000;
		
		//carry end time over
		_start = end;		
		return duration;
	}
	
	/**
	 * Measures and returns the time since the last start() or stop() invocation,
	 * restarts the measurement, and prints the last measurement to STDOUT.
	 */
	public void stopAndPrint()
	{
		double tmp = stop();
		
		System.out.println("PARFOR: time = "+tmp+"ms");
	}
	
}
